A study by the Groundwater Survey and Development Agency (GSDA) has revealed that paver-blocks are adversely affecting the recharging of groundwater levels in the city.

A study by the Groundwater Survey and Development Agency (GSDA) has revealed that paver-blocks are adversely affecting the recharging of groundwater levels in the city.

The civic corporation had asked the agency to conduct a survey for this matter.

“Extensive use of paver blocks for footpaths and approach roads affects the rainwater seepage,” said S.K.Gupta, former regional deputy director of the Groundwater Survey & Development Agency, Belapur, and a senior expert of the two-member GSDA committee, which was appointed to identify spots where new borewells could be dug. Gupta said that the paver-blocks, which are made of cement, are 4 to 5 inches thick. The interlocking of blocks allows only five per cent of the run-off water to percolate down, whereas on a mud track percolation levels were up to 40-45 per cent.

The civic body started using paver blocks since 2000-2001 because the laying of paver-blocks takes less time compared to other road surfacing options.

The blocks are usually used at high-traffic junctions.

“Exploiting ground water sources without recharging them will lead to a major problem in the future,” added Gupta.

“If the water table is not recharged adequately, it will facilitate the sea water to seep in and that in turn will make the ground water non-potable."

Gupta said that groundwater levels in suburbs such as Andheri (East), Malad (East) and Goregaon are over exploited and that the civic body should restrict the depth of the borewells that are now 400 ft deep.